In nanotechnology the term “nano” means that the relevant dimension is less than 100 nm. This implies that the 3D nanostructure and substructures may be typically a few microns large, but would be much smaller. In this application the term “nano” also encompasses structure with a relevant dimension up to 100 microns, preferably up to 50 microns or up to 10 microns. The lower limit is about 1 nm, preferably about 5 or 10 nm.
Several fabrication strategies have been developed to define sub-micron features without the need for nano lithography. These include edge lithography to create 2D-confined nanochannels and nano-ridges (see N. R. Tas, J. W. Berenschot, P. Mela, H. V. Jansen, M. Elwenspoek, A. van den Berg, “2D-Confined Nanochannels Fabricated by Conventional Micromachining”, Nano Lett., 2 (2002), pp. 1031-1032, and J. Haneveld, E. Berenschot, P. Maury, H. Jansen,“Nano-ridge fabrication by local oxidation of silicon edges with silicon nitride as a mask”, J. Micromech. Microeng., 16 (2006), pp. S24-S28). Another fabrication strategy includes the use of stress induced retardation of oxide growth in corners to create nano-apertures (See A. Vollkopf, O. Rudow, M. Muller-Wiegand, G. Georgiev, E. Oesterschulze, “Influence of the oxidation temperature on the fabrication process of silicon dioxide aperture tips”, Appl. Phys. A, 76 (2003), p. 923-926),and low temperature oxidation and selective etching (LOSE) to create an aperture at the apex of a pyramidal tip (see P. N. Minh, T. Ono, and M. Esashi, “Non-uniform silicon oxidation and application for the fabrication of aperture for near-field scanning optical microscopy”, Appl. Phys. Lett., 75 (1999), pp. 4076-4078.
Corner lithography was introduced and used to create a nano wire pyramid (see E. Sarajlic, E. Berenschot, G. Krijnen, M. Elwenspoek, “Fabrication of 3D Nanowire Frames by Conventional Micromachining Technology”, Transducers '05 [Digest of techn. Papers 13th Int. Conf. on Solid-State Sensors, Actuators and Microsystems], pp. 27-29).
Corner lithography is based on the material that is left in sharp concave corners after conformal deposition and isotropic etching. If t is the thickness of the deposited layer, α is the angle of the sharp concave corner, and R is the isotropic thinning distance, then the remaining material has a thickness w), given by:w=α−R=t/sin (α/2)−R 
The remaining material in the corners is referred to in IC fabrication as “stringers” and is usually considered undesirable. In corner lithography they either constitute the structural material of wire structures and tips, or are used as a masking material in subsequent fabrication steps. The general fabrication method consists of a few basic steps: (1) mold fabrication, (2) conformal deposition of the structural material, (3) isotropic thinning of the structural layer, nanowires remain in sharp concave corners and (4) removal of the mold.